High-Dose DHA Fails to Improve Cognition in 225 At-Risk Adults Over 2 Years

3 articles · Updated · Medical News Today · Jun 23

A 2-year randomized placebo-controlled trial found high-dose DHA supplements did not improve cognition or brain changes in 225 older adults at risk for dementia who completed the study.
365 participants were originally randomized, and DHA raised cerebrospinal fluid and blood DHA levels by 6 months, showing the supplement reached the brain without translating into measurable cognitive benefit.
Nearly half the participants carried the APOE ε4 Alzheimer’s risk allele, but researchers still found no meaningful cognitive advantage for carriers or non-carriers; safety outcomes were similar to placebo.
A 38% dropout rate—largely tied to COVID-19—plus missing data and a relatively young, atypical prevention population limited the study’s power and generalizability.
The findings argue against using high-dose DHA alone to prevent dementia and instead support broader brain-health measures such as diet, exercise, sleep, and vascular risk control.